The popular Facebook site has started asking the hundreds of millions of users of its cell phone application to enable its new Photo Sync option, a setting that will automatically upload every image taken with a mobile device to the social network’s vast data servers.

Once Photo Synch is enabled, each and every image taken by a cell phone’s camera is automatically sent to Facebook’s servers and uploaded to a private album for that user to later log-in and review. Should the user then decide they want certain pictures to go public, a click of the mouse from their computer will allow for the image to be made viewable to a select circle of friends; if no action is taken, the image will remain reserved only for the person who owns the profile — and Facebook.

Even if a Facebook user who’s enabled the website’s new Photo Sync service choses to keep all images private, those personal pictures are still sent over to the social networking site and stored on their computers. From there, Facebook can still steal the image’s geolocation data and use it to keep track of where its users are and whom they’re posing with.

Writing for The Point Daily, Alex Weiber says the roll-out of Photo Sync “will enable Facebook to build up a massive database from the information users are automatically providing to the company such as where they have been, and with whom.” Because Photo Sync allows every image taken with a mobile device to be automatically uploaded, that also means that candid pictures taken without a person’s knowledge can be captured and sent to the company’s servers, then perhaps plugged into Facebook’s complex facial recognition algorithm that can identify a user based on biometric information.

“[I]f someone takes a photograph of you without your permission it will be automatically uploaded to Facebook – you may demand that they delete the photo off their phone, but will it also have been removed from their private Facebook album?” asks Graham Cluley of Sophos Security.

Ewan Spence, a technology contributor for Forbes, points out the problems that might not be resolved until too late.

“And while the synced folder in Facebook will be ‘private’ I find it hard to trust Facebook’s constantly evolving privacy settings to keep these images truly private,” writes Spence.

“Privacy is clearly at the very back of the Facebook's mind when creating an application that enables this kind of uploading of photographs to be easier when it, in fact, it should be made more difficult,” adds Emma Carr, the deputy director with civil liberties group Big Brother Watch. “This provides a stark warning about the loss of control experienced once you have installed an application to your mobile phone.”

Facebook began advertising its Photo Sync service with mobile users this week and has not yet released any figures detailing the number of users that have enrolled in the program. Recent figures, however, indicate that Facebook’s mobile app is used by more than 200 million customers each month, and around 300 million images are uploaded to its servers each day.